Pressure control as an effective method to modulate aggregative growth of nanoparticles

Recent studies suggested that the interactions between particles can induce aggregative nucleation and growth processes beyond those predicted by the traditional LaMer model of nanoparticle formation, but their nucleation and growth processes are still unclear. Here, we report a simple way to control the interaction between nanoparticles by manipulating the oleylamine (OAm) adsorbed on the surface of the nanoparticles. The size distributions of Ag nanoparticles produced at different reaction pressures were monitored as evidence for aggregative growth. From these kinetic data, the aggregative nucleation rate (Γ) of primary Ag nanoparticles under a 0.01 MPa was demonstrated to be faster than that under atmospheric pressure. This leads to a higher uniformity of Ag nanoparticles in a shorter time (10 min) than that achievable with previous methods. Furthermore, Ag nanoparticles supported on TiO₂ exhibited a remarkable performance in the catalytic reduction of 4-nitrophenol (4-NP). After 4 min, 4-NP was completely reduced into 4-aminophenol (4-AP).